Decorative lighting, such as seasonal holiday lighting, generally includes decorative light strings, lighted trees, lighted decorative sculptures and other such lights and lighted objects. Such decorative lighting often comprises one or more strings of lights constructed of multiple wires, lamp assemblies and an electrical connector or power plug. Wires used in decorative lighting typically include an electrical conductor surrounded by an insulating material. The electrical conductor usually comprises multiple, individual strands of copper conductors. For example, a typical 50 light string of incandescent Christmas lights may be constructed using 22AWG wire that includes 16 individual copper strands twisted together and covered with an insulating polymer material, such as polyvinyl chloride (PVC).
To ensure safety, such wiring as used in decorative lighting applications may be required to meet various standards and requirements relating to both electrical and mechanical performance. For example, wires may be subject to dielectric testing, tensile-strength testing, breakage testing, cold temperature bending, flammability testing, and so on. From a mechanical perspective, some important and often-tested wire characteristics include tensile strength, breakage strength, and elongation. Not only does a decorative light string need to be able to conduct electricity safely, but it also needs to withstand physical abuse with limited risk of breakage. Breakage, including breakage of any portion of the wiring, could result in shock or electrocution to persons coming into contact with the decorative lighting or structures touching the decorative lighting, such as a tree.
One simple way to increase the mechanical integrity of wiring is to rely on relatively large gauge wiring. For example, while a 22AWG wire may be sufficient to safely conduct the expected electrical current of a light string, a 20AWG wire may actually be used to increase mechanical strength. However, while simply increasing the wire gauge may provide mechanical strength, the material cost to use oversized wire generally outweighs the resulting benefits.
Another known and commonly-used method of increasing mechanical strength of a decorative light string is to twist pairs of wires together. While this technique does not increase the mechanical strength of an individual wire, twisting two wires together, such as a first polarity wire and a second polarity wire, mechanically strengthens the overall decorative light string along its length. Such a known arrangement is depicted in FIG. 1, which illustrates a typical “twisted-pair” light string. In the light string of FIG. 1, the wires L1, L2, and L3 of the light string are twisted along the length of the light string. As such, if opposing forces were applied to the light string, for example pulling power plug 1 and end connector 2 in opposite directions, the twisted pairs of wires are stronger than single wires, and the likelihood of a wire breaking is decreased.
Referring to FIG. 2, a portion of a prior art net light is depicted. The net light depicts a second known method for strengthening decorative light strings, namely, wrapping a non-conductive, reinforcing strand about each individual conductive wire or wire segment. For example, the prior art net light of FIG. 2 includes non-conductive reinforcing strands 211 and 212 wrapped or twisted about multiple individual wires 13 that connect the various lamp assemblies 12. Should a portion of the net light be subject to pulling, the reinforcing strands serve to diminish the possibility that any individual wire will break.